Iranian Foreign Minister Javad Zarif, centre, arrives with US Secretary of State John Kerry, background centre right and European Union High Representative Federica Mogherini, second right, to make a statement at the Swiss Federal Institute of Technology, or Ecole Polytechnique Federale De Lausanne, in Lausanne, Switzerland, Thursday, April 2, 2015, after Iran nuclear program talks finished with extended sessions. The United States, Iran and five other world powers on Thursday announced an understanding outlining limits on Iran's nuclear program so it cannot lead to atomic weapons, directing negotiators toward achieving a comprehensive agreement within three months. AP

Iranian Foreign Minister Javad Zarif, centre, arrives with US Secretary of State John Kerry, background centre right and European Union High Representative Federica Mogherini, second right, to make a statement at the Swiss Federal Institute of Technology, or Ecole Polytechnique Federale De Lausanne, in Lausanne, Switzerland, Thursday, April 2, 2015, after Iran nuclear program talks finished with extended sessions. The United States, Iran and five other world powers on Thursday announced an understanding outlining limits on Iran's nuclear program so it cannot lead to atomic weapons, directing negotiators toward achieving a comprehensive agreement within three months. AP

Iran has agreed to shut down two-thirds of its nuclear enrichment program and accept international inspections that experts say are likely to cripple any attempt to make a nuclear weapon in return for the lifting of economic sanction imposed by the United States and its allies, according to a framework agreement announced Thursday.

The agreement, which still must be ratified by the negotiating nations by June 30, would impose its toughest restrictions for 15 years, with the severest lasting 10 then eased during the final five. U.S. Secretary of State John Kerry pointed out that contrary to recent news accounts, the deal has no expiration date.

“Robust inspections of Iran’s uranium supply chain will last for 25 years,” according to a summary of the agreement distributed by the State Department.

Iran would remain a member of the Nuclear Non-Proliferation Treaty, which prohibits the development of a nuclear weapon.

Speaking from the White House, President Barack Obama hailed the agreement, saying it would “shut down Iran’s path to a bomb” made from either uranium or plutonium.

“This deal is not based in trust,” he said. “It is based on unprecedented verification.”

He also challenged Congress to give the agreement serious consideration and approach it without partisan politics.

“These are matters of war and peace,” he said, noting that the agreement was not a bilateral deal between the United States and Iran but a deal between Iran and six world powers and the European Union. “If Congress kills this deal, the international community will blame the United States,” Obama said.

Experts reviewing the deal said they were surprised by its limitations on Iran, which include limiting its enrichment activities to a single site at Natanz, ending those activities at a second site at Fordow, and re-engineering a third site at Arak so that its reactor no longer would produce bomb-grade plutonium.

“It’s positive,” said Shahram Chubin, a nonresident senior associate at the Carnegie Endowment for International Peace’s Nuclear Policy Program.

United Nations Secretary-General Ban Ki-moon congratulated the countries on the tentative accord, which he said “will provide for substantial limits on Iran’s nuclear program and for the removal of all sanctions” on Iran.

“It will respect Iran’s needs and rights while providing assurances to the international community that its nuclear activities will remain exclusively peaceful,” he said.

As expected, Israel denounced the tentative deal. In a statement attributed to “government officials,” Israel contradicted Obama’s assertion that a completed deal would make “our world safer.”

“If an agreement is reached on the basis of these framework guidelines it will be a historic mistake that will make the world much more dangerous,” the statement said. “The framework gives international legitimization to Iran’s nuclear program whose sole aim is the production of nuclear bombs. Iran will retain broad nuclear capabilities: it will continue to enrich uranium, it will continue research and development of centrifuges, it will not close a single one of its nuclear facilities, including the underground facility at Fordow.”

The statement continued, “The alternative to a bad deal is not war, but another deal that will significantly dismantle Iran’s nuclear infrastructure and require that it stop its aggression and terror in the region and the world.”

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– Iran has agreed to reduce its operating centrifuges from the about “19,000 installed today to 6,104 . . . with only 5,060 of these enriching uranium for 10 years.” The surplus centrifuges are to be delivered to the International Atomic Energy Agency, which will store them. They will be returned to Iran only as replacements for broken ones.

– Iran’s operating centrifuges will be first-generation, and therefore less efficient, machines.

– Iran agreed to “not enrich uranium over 3.67 percent (of U-235) for at least 15 years.” In recent years, Iran has worried the international community by enriching some uranium to 20 percent U-235. To make a bomb, uranium must be enriched to 90 percent purity. The agreed-to percentage is adequate for nuclear power production.

– For the next 15 years, Iran will cut its stockpile of about 22,000 pounds of low-enriched uranium to 661 pounds.

The fact sheet said that “Iran’s breakout time line – the time that it would take for Iran to acquire enough fissile material for one weapon – is currently assessed to be two to three months. That time line will be extended to at least one year, for duration of at least 10 years, under this framework.”

In exchange for agreeing to what the negotiating world powers called a historic level of oversight, Iran would see most of the economic sanctions imposed lifted, though some imposed by the United States would remain. The suspensions of the sanctions would take place “after the IAEA has verified that Iran has taken all of its key nuclear-related steps.”

Experts this week have estimated that the lifting of sanctions could mean an infusion of $60 billion a year into what is now a struggling Iranian economy. German news outlets have reported that Germany alone would expect to do as much as much as $10 billion of trade a year with Iran if the sanctions were lifted.

Getting the sanctions lifted was the primary goal of the Iranians coming into these negotiations. Even so, they agreed to a so-called “snap-back” provision that would reimpose the sanctions “if at any time Iran fails to fulfill its commitments,” according to the fact sheet.

“The architecture of U.S. nuclear-related sanctions on Iran will be retained for much of the duration of the deal and allow for snap-back of sanctions in the event of significant non-performance,” the U.S. summary said.

According to a joint statement that was read to reporters first in English by the European Union’s representative to the talks, Federica Mogherini, and then in Persian by Iranian Foreign Minister Javad Zarif, Iran would be permitted to enrich uranium only at its facility at Natanz.

Another facility, at Fordow, “will be converted from an enrichment site into a nuclear, physics and technology center,” the statement said. “There will not be any fissile material at Fordow.”

As for Iran’s reactor at Arak, “an international joint venture will assist Iran in redesigning and rebuilding a modernized heavy water research reactor . . . that will not produce weapons-grade plutonium. There will be no reprocessing and the spent fuel will be exported.”

Maintaining some facilities at Fordow and Arak was an important point for the Iranians, and Zarif made a point that Iran had not given up its nuclear program.

“Facilities won’t be closed and Iran will continue to enrich uranium,” he said.

The deal came after eight days of intense talks in this chic mountain city along the edge of Lake Geneva. A deal had appeared on the brink of collapse at several times during negotiations, especially after a self-imposed deadline of March 31 had passed without a full agreement.

The negotiators dealing with Iran were referred to as the P5+1 – the five permanent members of the United Nations Security Council – China, France, Russia, the United Kingdom and the U.S., plus Germany – and the European Union.

British Foreign Secretary Philip Hammond, who spent the past week repeating that no agreement was better than a bad agreement, said this was a good agreement.

“This is well beyond what many of us thought possible even 18 months ago and a good basis for what I believe could be a very good deal,” he said in a statement. “But there is still more work to do. The fine detail of any deal will be very important.”

Paul Kawika Martin, political director of the anti-nuclear weapons group Peace Action, praised the agreement.

The deal, he said in a statement, will “ensure (Iran) will not produce a nuclear weapon making the U.S. and the world a safer place. This agreement promises to keep Iran at least a year away from having the fissile material needed to make a crude nuclear weapon. Without an agreement, that time line shrinks to three months and the threat of war increases dramatically.”

McClatchy special correspondents Joel Greenberg in Jerusalem and John Zarocostas in Geneva contributed to this report.